Consistent patterns in leaf lamina and leaf vein carbon isotope composition across ten herbs and tree species

Abstract

Wide-spread post-photosynthetic fractionation processes deplete metabolites and plant compartments in (13)C relative to assimilates to varying degrees. Fragmentation fractionation and exchange of metabolites with distinct isotopic signatures across organ boundaries further modify the patterns of plant isotopic composition. Heterotrophic organs tend to become isotopically heavier than the putative source material as a result of respiratory metabolism. In addition fractionation may occur during metabolite transport across organ and tissue boundaries. Leaf laminae, veins and petioles are leaf compartments that are arranged along a gradient of increasing weight of heterotrophic processes and along a transport chain. Thus, we expect to find consistent patterns of isotopic signatures associated with this gradient. Earlier studies on leaves of Fagus sylvatica, Glycine max, and Saccharum officinarum showed that the organic mass and cellulose of major veins or petioles were consistently more positive than the respective fraction in leaf laminae. The objective of the current study was to assess whether this pattern can be detected in a greater set of plant species. Leaves from ten species were collected in the summer of 2006 outdoors and in glasshouses. Leaf laminae including small veins were separated from the major veins and the isotopic signatures of the organic mass, and the soluble and non-soluble fractions were measured for laminae and veins separately. The organic mass, and the soluble and non-soluble fractions of leaf laminae, were depleted in (13)C relative to the veins in all cases. A general trend for the signature of organic mass being more depleted in (13)C than the soluble fraction is in accordance with well-known patterns of fractionation between metabolites.

Changes in 13C/12C of oil palm leaves to understand carbon use during their passage from heterotrophy to autotrophy

“…This stage was maintained until rank 5, and the leaves during this period still showed a vertical orientation in the crown. Thereafter, an important increase in leaf sugar contents was observed, rapidly reaching a plateau and stayed stable until rank 30, probably 13 17 This could be due either to the heterotrophy of the veins (the rachis in the case of the oil palm leaf) and petioles compared with laminae (leaflets) or probably to a higher anaplerotic activity in petioles and rachises similar to the reported data, for instance the C 4 -like functioning of the vascular photosynthetic cells in celery and tobacco petioles, 40 and the high level of PEPc in the young twigs of beech and some other tree species. 41 This could be one of the main reasons for 13 C-enrichment in the veins, petioles and rachises of C 3 plants.…”

“…Recent studies [13][14][15][16][17] on carbon isotope discrimination during post-photosynthetic processes have strengthened the idea that allocation pathways could be deduced from the observation of isotopic signature variations among organs. Concerning carbon allocation, behind each organ growth and development there are carbon fluxes between autotrophic sources and heterotrophic sink tissues.…”

Opposite carbon isotope discrimination during dark respiration in leaves versus roots – a review

“…2‰ compared with tree trunks. A difference in carbon isotope composition is also observed between different tissues of a given organ; for example, leaf lamina were shown to be 13 C‐depleted compared with leaf ribs in different herbs and woody species (Badeck et al ., and references therein). Heterotrophic leaves (before photosynthetic onset) are 13 C‐enriched compared with green autotrophic leaves as well (Bathellier et al ., ; Lamade et al ., ).…”

Changes inδ13C of dark respired CO2and organic matter of different organs during early ontogeny in peanut plants

“…A difference in carbon isotope composition is also observed between different tissues of a *Corresponding author. Email: jaleh.ghashghaie@u-psud.fr given organ, for example, leaf lamina were shown to be 13 C-depleted compared with leaf ribs in different herbs and woody species (see [5] and references therein). Heterotrophic leaves (about to be emerged and not yet green) are 13 C-enriched compared with green autotrophic leaves as well [6,7].…”